Can't move the viewport after updating from 2.69 to 2.78
It's possible that not all of the settings were copied over from your old blender version into 2.78 when you installed it.

As far as I know, the option to move the mouse with Option (or Alt)+Click and Drag isn't enabled by default, but can be enabled by checking the 'Emulate 3 Button Mouse' box under the Input panel of the User Preferences.